Day something?

May 18th, 2013

I am losing track of the days now. The other night I went and worked on the new middle section. It’s not totally done but is close now. Today (Saturday) I went and visited Woody to borrow his guillotine to cut up welding rods. I just cut strips of aluminium so they were square section rods. About 90 lengths all up. When welding we use this as filler rod since it is the same as the metal you’re welding. When the welds are done everything is all the same material so it is really just one big piece.

20130518_123754 Cutting welding rods.

The rods are wiped through a scotch pad to clean them then painted with flux. The excess flux is flashed off in a flame. The flux soaks up water from the air so if you leave the rods for a while they end up dripping wet again.

20130518_133318 Preparing rods.

I prepared six rods at a time ready for welding.

When welding the flux gives off a bright orange flame. To counter this we use blue filtered goggles. I was actually using a full face shield with blue gel taped to it. This works great without fogging up. It’s a bit hard to photograph the difference but below you can see it when Joss was demonstrating the welding for me. I took one picture normally then another through my blue face mask. You can see how the blue cuts out the orange flame. In practice the torch flame doesn’t appear as bright as in the picture below. The camera over exposes it and makes it seem brighter.

20130518_143234 20130518_143312 Blue filter.

In practice you can see everything very clearly. You need to to see what the aluminium is doing. To do the weld you heat the aluminium with the gas flame and you watch for the subtle change on the surface as it gets hot enough. The only way I can describe it is it gets a sheen or a wetness to it. Shortly after that it is ready to add the filler rod. Everything has to be done quickly or else you just melt a hole.

First though you must tack together the pieces you are welding. The skin was taken off the frame and propped up and the pieces to weld clamped together in their correct positions. First though the edges are cleaned with the scotch pad and fluxed. Then the tacks are done. These are just single spots of weld along the edges to join them. You start at one end and join that then simply pull the pieces into the right position by hand to get them to line up.  After tacking you  hammer the edges to make sure they line up nicely then you then go fill in between the tacks with weld.

20130518_163510 Tacks.

The welding is done one little blob at a time. You hold the filler rod on the edge of where the weld will be then heat up the spot and the rod will melt into it causing a little bump of metal. The welds are a series of little bumps like this but you overlap them to keep the weld continuous. You can’t do it in one continuous go though as the metal gets too hot and will melt and you will end up blowing a big hole in the panels. So you do a spot, wait a few seconds (I found counting to 3 worked for me) with the flame off the weld then do the next little bit. You can get into a real rhythm doing this.

But you have to be careful not to get carried away. You do not want holes. Holes are bad as it would mean adding in a  patch which is a lot of work. If it looks like things are going wrong you immediately move the torch away and wait for things to cool down. You can see when the metal is getting close. The changes are subtle. The metal sags and almost looks like it is crusting over. You must then immediately remove heat.  Luckily I avoided any holes!

The first weld I did was the longest on the car, the  front left weld (there are 9 in total to do). This took me about an hour to do as I was learning as  I went. I then did the front right weld which only took 25 minutes (although it is a little shorter). It takes a lot of concentration and a steady hand too. When you get to the ends a big clamp over the very edges helps sink some of the heat. If you try to weld right to the edge without a heatsink it will get too hot and you’ll just burn a hole in the edge.

Since we use rod to feed into the weld you end up with much more metal there than needed. The weld looks lumpy as hell but then the extra material gets ground then filed off. In theory the weld should be invisible after doing this. As soon as the weld is done all the flux is scrubbed off with a scotch pad and water. It’s nasty corrosive stuff. All tools such as  hammers, dollies  and clamps that come into contact with it are also well cleaned after use.

20130518_170855 20130518_182630 First real weld.

Tomorrow I will tidy up these first welds then hammer the bends so the front half of the skin sits properly on the car. Then I can weld the two sides of the tail together and join them to the front.

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